/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.runners.core.triggers;



import com.bff.gaia.unified.sdk.transforms.GroupByKey;

import com.bff.gaia.unified.sdk.transforms.windowing.BoundedWindow;



/**

 * A {@link TriggerStateMachine} which never fires.

 *

 * <p>Using this trigger will only produce output when the watermark passes the end of the {@link

 * BoundedWindow window} plus the allowed lateness.

 */

public final class NeverStateMachine extends TriggerStateMachine {

  /**

   * Returns a trigger which never fires. Output will be produced from the using {@link GroupByKey}

   * when the {@link BoundedWindow} closes.

   */

  public static NeverStateMachine ever() {

    // NeverTrigger ignores all inputs and is Window-type independent.

    return new NeverStateMachine();

  }



  private NeverStateMachine() {

    super(null);

  }



  @Override

  public void onElement(OnElementContext c) {}



  @Override

  public void onMerge(OnMergeContext c) {}



  @Override

  public boolean shouldFire(TriggerStateMachine.TriggerContext context) {

    return false;

  }



  @Override

  public void onFire(TriggerStateMachine.TriggerContext context) {

    throw new UnsupportedOperationException(

        String.format("%s should never fire", getClass().getSimpleName()));

  }

}